Clinicians and researchers now agree that type 2 diabetes is a condition that can affect the pediatric population. The incidence of type 2 diabetes in children has increased dramatically over the past ten years, especially in African American, American Indian, and Hispanic populations. This increased incidence has been linked to the increasing prevalence of childhood obesity and sedentary lifestyle. Type 2 diabetes in children represents an emerging epidemic in which African American, American Indian, and Hispanic children are disproportionately represented. There is a need for controlled clinical studies to evaluate the safety and utility of metformin in children with type 2 diabetes since the standard of care for children with all types of diabetes has previously been considered to be insulin as the sole FDA approved agent. This study will serve to assess metformin plus insulin in comparison to insulin monotherapy for the care of children with type 2 diabetes of moderate severity. It will also serve to show the safety of adding metformin to insulin in adolescents with type 2 diabetes. In addition, this study will provide pharacokinetic data for metformin therapy in adolescents.